Paper containers for liquids are widely used for fruit beverages, liquid beverages such as tea, coffee, milk beverages, soup, and alcoholic beverages such as sake and shochu. Examples of the shape of such a container include a gable top shape, a brick shape and a cylindrical shape.
For example, in manufacturing a brick-shape paper container for liquids, scores for forming the container are applied to a packaging material formed of a paper layer with a thermoplastic resin layers being provided on the front and back surfaces thereof, and an edge protection tape is applied to the end portions of the packaging material. Then, the packaging material is formed into a tubular shape, and the longitudinal end portions of the packaging material are overlapped and bonded to each other, thereby forming a packaging material having a tubular shape. Subsequently, the lower end portion of the tubular packaging material is sealed in the transverse direction, and then subjected to submerged sealing for sectioning in the state of being filled with liquid contents, followed by forming into a three-dimensional shape, thereby providing a paper container.
To seal the packaging material in the transverse direction, the packaging material is pressed and vibrated by a horn (vibrating side) attached to a converter (ultrasonic oscillator) that converts electric energy into mechanical vibration energy and an anvil (vibration receiving side), to melt the thermoplastic resin layers on the surfaces of the packaging material with heat generated at the package material interface (see PTLs 1 and 2).
Known documents are shown below.